Minimal important difference of the Migraine Disability Assessment (MIDAS): Longitudinal data from the DMKG Headache Registry.

Background: The Migraine Disability Assessment (MIDAS) is widely used. However, there are limited data on how much a reduction in the MIDAS score indicates a change that matters to the patient.

Methods: Data from the DMKG (i.e. German Migraine and Headache Society) Headache Registry were used to determine the minimal important difference (MID) of the MIDAS, using the Patient Global Impression of Change (PGIC) as anchor and applying average change and receiver operating characteristic curve methods.

Results: In total, 1218 adult migraine patients (85.6% female, 40.2 ± 12.8 years, baseline MIDAS 44.2 ± 47.4, follow-up MIDAS 36.5 ± 45.3) were included. For patients with baseline MIDAS >20 (MIDAS grade IV, n = 757), different methods using PGIC "somewhat improved" as anchor yielded percent change MIDs of the MIDAS between -29.4% and -33.2%. For baseline MIDAS between 6 and 20 (grades II and III, n = 334), using PGIC "much improved" as anchor, difference change MIDs were between -3.5 and -4.5 points.

Conclusions: Based on the above results, we estimated the MID of the MIDAS at -30% for patients with a baseline MIDAS >20, and at -4 points for those with a baseline MIDAS of 6-20, for a tertiary headache care population.

Trial registration: The DMKG Headache Registry is registered with the German Clinical Trials Register (DRKS 00021081).